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Scan for outdated or missing drivers - takes under a minuteDriver Scan →Repair Windows errors before they cause bigger problemsFix Now →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Define your app, PostgreSQL, and Redis as services in compose.yaml. From the web container, connect to the other services by their Compose service names—db and redis—not localhost. Add healthchecks and long-form depends_on conditions if the app must wait for those services to become ready, and store PostgreSQL data in a named volume.
Define the three services in compose.yaml
This starting template uses Docker’s documented PostgreSQL and Redis healthcheck patterns. Replace the build context, environment variable names, credentials, and image tags with values appropriate to your application. The postgres:18 and redis:alpine tags are examples, not universal version recommendations; confirm compatibility with your app and deployment target.
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services:
web:
build: .
ports:
- "8000:8000"
environment:
DATABASE_URL: postgresql://app:${POSTGRES_PASSWORD}@db:5432/app
REDIS_URL: redis://redis:6379
depends_on:
db:
condition: service_healthy
redis:
condition: service_healthy
db:
image: postgres:18
environment:
POSTGRES_DB: app
POSTGRES_USER: app
POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
volumes:
- postgres_data:/var/lib/postgresql/data
healthcheck:
test: ["CMD-SHELL", "pg_isready -U $${POSTGRES_USER} -d $${POSTGRES_DB}"]
interval: 10s
timeout: 10s
retries: 5
start_period: 30s
redis:
image: redis:alpine
healthcheck:
test: ["CMD", "redis-cli", "ping"]
interval: 5s
timeout: 3s
retries: 5
start_period: 10s
volumes:
postgres_data:How the connections work
Compose creates a network for the services. The web app reaches PostgreSQL at host db and Redis at host redis, using each service’s container port. In this example those ports are 5432 and 6379. The 8000:8000 mapping publishes the web service’s port 8000 on the host; it does not change how containers address one another.
The connection-string formats are examples. Use the environment variable names and URL syntax expected by your framework and configure any required database name, username, password, TLS, or other options accordingly.
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Why the PostgreSQL healthcheck uses $$
Compose normally interpolates dollar-sign variables while it reads the file. Doubling the dollar sign in $${POSTGRES_USER} and $${POSTGRES_DB} defers expansion to the shell inside the container, where those environment variables are available. The check runs pg_isready with the configured database user and name.
Start the stack and check its state
-
From the directory containing
compose.yaml, start and build the services:Rank #2
docker compose up --build -
In another terminal, inspect service status:
docker compose ps -
Follow logs from the app and its dependencies:
docker compose logs -f web db redis
The Redis check uses redis-cli ping, which tests whether Redis responds to that probe. A healthy status for either dependency means its configured check succeeded; it does not prove that the web app’s credentials, schema, migrations, or application-level operations are correct.
Understand startup order versus readiness
Short-form depends_on controls startup order, but it does not make Compose wait for a dependency to become ready. Docker documents that Compose waits for a container to be running—not ready—unless readiness is handled separately. With a healthcheck and condition: service_healthy, Compose waits for the dependency’s configured healthcheck to pass before starting the dependent service. See Docker’s startup-order guide and service reference.
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Healthchecks are bounded probes, not an application readiness guarantee. Their result depends on the command and timing settings you configure. Your app should still handle failed connections and, where appropriate, retry operations if a dependency becomes unavailable after startup.
Keep PostgreSQL data across container removal
The postgres_data named volume is mounted at PostgreSQL’s data directory. It keeps database files outside the container’s writable layer, so removing and recreating the container does not by itself erase the volume’s contents.
To stop the services and remove their containers and default network while retaining named-volume data, run:
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Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstalldocker compose downDo not add -v when you want to preserve the volume. Removing volumes can delete persisted state, so check what data the project needs before doing so. Docker’s Compose Quickstart demonstrates the volume and data lifecycle.
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PostgreSQL initialization happens on an empty data directory
The official PostgreSQL image’s initialization environment variables and initialization scripts apply when the data directory is first initialized. Changing POSTGRES_PASSWORD, POSTGRES_USER, or POSTGRES_DB later does not reinitialize an existing volume. The image documentation also notes that if an initialization script fails after the data directory has been initialized, restarting the container does not automatically resume the remaining scripts. Diagnose the failure and choose a deliberate recovery plan rather than assuming a restart will rerun initialization. See the official PostgreSQL image documentation.
Decide whether Redis data should persist
A Redis volume is not included in this template because the right policy depends on Redis’s role. If it is only a cache whose contents can be rebuilt, disposable data may be appropriate. If it holds queue state or other data the application cannot afford to lose, decide on persistence, backups, and recovery deliberately; simply adding a volume does not define a complete policy. Docker’s Quickstart shows a Redis named-volume example, but your application’s requirements determine whether and how to use one.
Protect credentials and plan for the target environment
The example references POSTGRES_PASSWORD without embedding its value in the Compose file. For local development, provide it through an environment file excluded from version control or another suitable local mechanism. For deployment, use the secrets handling appropriate to that environment; Docker’s Node.js guide demonstrates Compose secrets. Never commit real credentials to a shared repository.
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A local Compose stack does not, by itself, provide a production security, backup, high-availability, monitoring, or disaster-recovery design. Select supported database and Redis versions, image tags, and migration strategies for the actual application and deployment target.
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